Transformer.



PATENTED SEPT. 15,v 190s..

R. R. WILEY. TRANSFORMBR.

APPLICATION FILED JAN. 24. 1903.

N0 MODEL.

NTED STATES :Patented September 15, 19033 PATENT Orrrcn.

TRANSFORM ER.

SPECIFICATION forming pent ef Lettersretent No. 738,864, aerea september 15, 1903. Application filed rennnny 24,1903. seniei 110.140.356. (No model.)

To a/ZZ wir/0771, it may concern,.-

Be it known that I, ROY RODNEY WILEY, a'

ductively transforming intermittent or alter-V natin g currents in one electrical circuit to intermittent or alternating currents in another electrical circuit, usually with a change of current and pressure. Such transformers as now built are usually provided with a core built of insulated soft-iron laminze, upon which core are wound one or more primaryI coils and one or more secondary coils. e The' number of turns of vWire inthe primary and secondary coils is usually made different in' order to get a ratio'of transformation which is not unity. Such a transformer when placed in continuous service for the purpose of inductively transferring alternating .currents from one circuit to another` is subject to an increase in temperature. Part of this heating of the transformer is due to the resistance of the transformer-conductors to the liow of current therethrough. On'account of thedecreased cost of construction it is desirable that the conductors forming the transformercoils be made of the smallest possible size; but opposed to this advantage gained in decreased cost is the disadvantage of a correspondinglyincreased resistance and correspondingly-increased heating effect.

rlhe heating of transformers has given rise to serious difficulty and inconvenience in the operation thereof due to the deterioration and breaking down of the necessary insulation when subjected to a high temperature. The materials which may profitably be employed for insulating purposes will not withstand more than a certain maximum degree of temperature without such consequent deterioration. There is, however, marked economy resulting in the operation of transformers at or only slightly below this maximum safel temperature, and afurther economy and improvement would reside in the provision of means whereby every part of every coil might lbe operated at orl slightly below this maximum safe temperature. In other Words, it is desirable that the temperature be substantially the same throughout the transformer.. In' order to prevent too great a rise in the temperature of commercial transformers,spe cial provision has been made to insure the proper cooling thereof. In some cases the radiation of heat from the transformer to the surrounding air has been relied upon to cool the coils. In other instances the transformer proper, as above described, has been immersed in a receptacle filled or partially illed withoil. The circulation of this oil around the transformer parts has been relied upon to convey heat from the coils to the transformer case or receptacle through which it has been conducted to the outside air. It will be apparent that with such methods of cooling an increased area of contact between the heated qparts of the transformer and the cooling medium will cause a corresponding increase in the cooling effect and a consequent decrease inthe transformer temperature.

In transformers of the prior art it may be stated that in general an increase in the area directly affected by the cooling medium tends to require a corresponding increase in the length of the magnetic circuit. Such an increase in the length of the magnetic circuit, on the other hand, tends to cause an ineiciency of the transformer and to increase its size and cost.

In order to maintain a substantially uniform temperature throughout the transformercoils, it is desirable that the inner conductors and parts be cooled to the same extent as the outer parts.

It is the object of my invention to provide a commercial transformer having a short magnetic circuit and at the same time a large total cooling area. It is further the object of my invention to provide a transformer having a substantially equal cooling area for each transformer-coil, whereby all the coils and all the conductors in each coil may operate at substantially the same economi al temperature, thus permitting the use of conductors of higher resistance than has heretofore been possible.

The construction of my improved transformer is such that only a small difference of potential exists between adjacent windings. In general I have provided a transformer of increased mechanical and electrical efficiency and of decreased cost of construction and operation.

I may attain the objects of my invention, preferably, by the provision of a laminatediron core of substantially rectangular crosssection having a suitable rectangular opening in the middle. vA core is thus provided having legs forming the four sides of an open rectangle. The conductors forming the transformer-windings are placed about the legs of this soft-iron core.

I find it desirable to make the windings in the form of so-called pancake-coils,7 each pancake-coil being separately wound and insulated before assembly with the other transformer parts. A number of these pancakewindings are preferably placed side by side on a single leg of the transformer-core. It is desirable that the coils placed on the core substantially fill the opening within the core, and within this opening the coils or the insulating materials covering the coils are in contact one with another. On the outside of the core the coils are spaced apart, thereby leaving an open space between three sides of adjacent coils. These open spaces permit the free access and circulation of the cooling medium, whereby a large area and an equal area of each coil is directly exposed to the cooling', effect of the lcooling medium.

In order that the transformer-coils may be well insulated and cheaply formed, I wind the conductors or turns forming any one coil each in a plane parallel with the planes through all the other conductors or turns forming the same coil. Such a coil may be described as a uniplanar-coil, in contradistinction to what may be terme( warped coils, in which a com plete turn cannot be made to lie in a single mathematical plane.

In addition to the equal and uniform cooling of the coils resulting from the above-described arrangement I iind that by winding the primary and secondary coils each in such a pancake-coil the difference in electrical potential between adjacent turns maybe very greatly reduced, thereby correspondingly reducing the liability of disruption of the insulation between adjacent turns.

I can more clearly describe my invention by reference to the accompanying drawings, in which- Figure l is a perspective view of a trailsformer embodying my invention. Fig. 2 is a plan view thereof, the coils on 011e of the legs being shown in cross-section.

I have shown a laminated-iron core 3, built up of layers of soft sheet iron or steel in the manner well known to those skilled in the art. On two opposite legs of the rectangular core thus formed I place the primary coils 4 4, which in this instance are shown of comparatively fine wire, and the secondary coils 5 5, which are of fewer turns and correspondinglycoarser wire. As well understood by those skilled in the art, the primary coils 4 may be connected in series or in series parallel with supply-mains leading from a suitable source of alternating current. The rectangular core 3 provides a single closed magnetic circuit for the lines of magnetic force set up by the current iiowing in the coils 4. In the present embodiment of my invention three such primary coils `are shown on each leg of the transformer,theintermediate spaces being partially occupied by two secondary coils. All of the coils are of the so-called pancake type, each being preferably wound upon a suitable form before assembly with the transformer core. As will be apparent from the drawings, the coils are comparatively short along their magnetic axes as compared with their thickness perpendicularly thereto. There is practically the same difference of potential between the ends of each turn of such a coil. It will be seen that in such a pancake-coil only comparatively few complete turns at any place are serially included in circuit between adjacent conductors,where by the difference in potential between such adjacent conductors is not great enough to readily break down the proper insulation thereof. I preferably employ such uniplanarcoils as heretofore described, the coils practically filling the opening in the core, within which opening the coils are brought into con- `tact one with another. At the outer sides of the transformer, however, these uniplanar pancake-coils are spaced apart, in the manner best illustrated in Fig. 2, leaving openings between three sides of the adjacent rectangular coils. Thus the cooling medium employed, whether it be air or oil, within a transformer-case has free and direct access to three faces of each of three sides of each coil. The fact that the coils are each wound with a comparatively small number of turns provides that no conductor is greatly removed from the surface of the coil, whereby the heat generated in an internal conductor is rapidly conveyed to the surface of the coil. It will be seen, furthermore, that in accordance with my invention all of the coils, both primary and secondary, are substantially equally eX- posed to the cooling effect of the cooling medium, the areas of the surfaces of all the coils in direct contact with'the cooling medium being equal.

There is a considerable advantage gained by the number and relative displacement of the primary and secondary coils, as shown in IOO the accompanying drawings. As previously stated, the primary coils may be connected either in series or in series parallel with transmissionmains in the manner familiar to those skilled in the art, while the four secondary coils may be connected in series to give a certain maximum pressure, in series parallel to give one-half the maximum pressure, or in parallel to give one-quarter the maximum pressure. Since each of the secondary coils is symmetrically placed with regard to the magnetic circuit and the primary inducingcoils, it will be apparent that under all arrangements of the circuit connections the magnetic induction and leakage will be perfectly balanced.

Vhile I have herein shown and described one particular embodiment of my invention, it will be apparent to those skilled in the art that many modifications and changes might protably be employed without departing from the spirit thereof, and I do not Wish to be limited to the precise disclosure herein set forth; but,

Having described my invention, I claim as new and desire to secure by Letters Patentl. In a transformer, the combination witha hollow rectangular iron core, ol. a plurality of uniplanar, primary and secondary coils on a leg of said core, adjacent coils being in contact with one another on one side of said leg and having an intervening space on another side of said leg, substantially as described.

2. In a transformer, the combination with a hollow rectangular iron core providing a single magnetic circuit, of a plurality of uniplanar, primary and secondary coils on a leg of said core, adjacent coils being in contact with one another on one side of said leg and having an intervening space on another side of said leg, substantially as described.

3. In a transformer, the combination with a hollow rectangular iron core providing a single magnetic circuit, of a plurality of sandwiched uniplanar, primary and secondary coils on a leg of said core, adjacent coils being in contact with one another on the inside of said leg, and having an intervening space on the outside of said leg, substantially as described. l

4i. In a transformer, the combination with a hollow rectangular iron core providing a single closed magnetic circuit, of a plurality of sandwiched uniplanar, primary and second ary coils on opposite legs of said core, adjacent coils being in contact with one another on one side of said leg, and having an intervening space on another side of said leg substantially as described.

5. In a transformer, the combination with a hollow rectangular iron core providing a single magnetic circuit, of a plurality of sandwiched uniplanar, primary and secondary coils on opposite legs of said core, adjacent coils being ,in contact with one another on the'insides of said legs and having an intervening space on the outsides of said legs, substantially as described.

6. In a transformer, the combination with a hollow rectangular iron core providing asingle magnetic circuit, of a plurality of sandwiched,'pancake primary and secondary coils V on a leg of said core, adjacent coils being in contact with one another on one side of said leg and having an intervening space on another side of said leg, substantially as de scribed.

7. In a transformer, the combination with a hollow rectangular iron core providing asingle closed magnetic circuit, of a plurality of sandwiched primary and secondary coils on opposite legs of said core, adjacent coils'being in contact with one another on the insides of said legs and having an intervening space on the outsides of said legs, substantially as described.

8; In a transformer, the combination with a hollow rectangular iron core providing a single magnetic circuit, of anumber of uniplanar pancake primary coils on each of two opposite legs of said core and uniplanarpancake secondary coils on said legs interposed between said primary coils, adjacent coils being in contact with one another on the inner sides of said legs and having an intervening space on the outer sides of said legs, substantially as described.

9. In a transformer, the combination with a hollow rectangular iron core, of a plurality of uniplanar, primary and secondary coils on a leg of said core, there being a greater space between adjacent coils at one side of said leg than at the other side of said leg.

l0. In a transformer, the combination with a hollow rectangular iron core providing a single magnetic circuit, of a plurality of uniplanar primary and secondary coils, on a leg of said core, there being a greater space be-v tween adjacent coils at one side of said leg than at another side of said leg.

ll. In a transformer, the combination with a hollow rectangular iron core providing a single magnetic circuit, of a plurality of sandwiched primary and secondary coils on opposite legs of said core, there being a greater space between adjacent coils at the outsides of said legs than at the insides of said legs.

12. In a transformer, thelcombination with a hollow rectangular iron core, providing a single magnetic circuit of more than two primary and secondary coils on each of two opposite legs of said core, said coils being in contact one with another at one side of each of said legs and having substantially equal areas exposed to a cooling medium.

13. In a transformer, the combination with a hollow rectangular iron core providing a single magnetic circuit of more than two primary and secondary coils on a leg of said core, said coils being in contact one with another at one IOO IIO

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side of said leg, and having substantially equal areas exposed to a cooling medium.

14. In a transformer, the combination with a hollow rectangular iron core providing` a single closed magnetic circuit, of a number of uniplanar pancake primary coils on each of two opposite legs of said core, and uniplanar pancake secondary coils on said legs interposed between said primary coils, there being a greater space between adjacent coils at i0 the outsides of said legs than at the insides orn said legs.

In Witness whereof l hereunto subscribe my name this 17th day of January, A. D. 1903.

ROY RODNEY VILEY. Vitnesses:

A. W. MARQUIS, I-l. BATES. 

